Military defense programs often employ tactical shelters to house radar transmitters, command and control centers, launching systems, tactical operations systems and the like. The shelters are enclosed structures. Openings, e.g. doors in the shelter provide for ingress and egress to the contents within the shelter or for electrical cable connections. For mobility, the shelters are typically mounted on a motor vehicle such as a high mobility multi-purpose wheeled vehicle (HMMWV) or a tractor-trailer.
Achieving and maintaining radiation shielding in these shelters is a critical but difficult task. Without sufficient shielding, electromagnetic interference and/or electromagnetic pulses (EMI/EMP) can disrupt radio transmissions, communications, and signals, and/or make them ineffective. Additionally, errant transmissions from the shelters can be traced, thus making the shelters subject to detection and action by adversaries. Typically then, such shelters are made of aluminum or aluminum alloys to provide a favorable combination of electromagnetic shielding in a lightweight structure.
The difficulty with aluminum or aluminum alloy shelters is that the shelter door frames or housings corrode over time, especially in corrosive environments including biological, chemical contamination and survivability (BCCS) environments encountered in the field. The dissimilarity of the materials, namely the aluminum shelter and the material of the gasket on the door which seals with the door frame, contributes to this effect. Consequently, performance and survivability are compromised.
Metal plating of the aluminum, for example, is not a practical and viable alternative because it is known that aluminum is galvanically incompatible with almost all other metals. Thus, in an attempt to eliminate this problem, existing designs apply metal spray coatings or metal frame spray compositions to the aluminum. The use of conventional metal spray coatings and compositions on the aluminum based shelters has proven to be less than satisfactory. Metal spray coatings do not have adequate corrosion resistant properties. The metal spray coatings are also galvanically incompatible with the aluminum, and the metal spray coatings typically utilized are also comprised of material dissimilar from the gasket on the shelter door. Thus, over time there is separation between the metal coating or composition and the aluminum. The frames for the shelter doors or panels are particularly susceptible to cracking, erosion and corrosion, especially the strike plates where the door gasket seals against the frame when closed. Therefore, because of the galvanic incompatibility and the dissimilarity between the metal spray coatings and the aluminum and/or the gasket material on the shelter door, shelters which utilize metal spray coatings do not adequately address the problem of decreased shielding effectiveness caused by corrosive attack and/or wear. This failure to provide adequate corrosion resistant properties over time leads to constant maintenance and costly repairs at best, and in the worst case, can lead to negative consequences in the field.